Study of Peak-load regulation characteristics of a 1000MWe S-CO₂ Coal-fired power plant and a comprehensive evaluation method for dynamic performance

In the new power system with large-scale grid-connection of intermittent new energy, the coal-fired power plants (CFPPs) play an important role of the ballast stone. In the process of grid-connection, CFPPs receive variable load instructions in real time. Higher peak-load regulation capacity and more flexible response for CFPPs are needed to provide a stable support to the power grid. The supercritical carbon dioxide (S-CO₂) cycle has better variable working condition performance, which may improve the flexibility of the CFPPs peak-load regulation process. To explore the peak-load regulation characteristics of the S-CO₂ CFPP, the variable load characteristics of a tri-compressions double-reheating intercooling (TC-DRH-IC) S-CO₂ CFPP under five control methods are studied. Furthermore, a comprehensive evaluation method for the dynamic performance is proposed. First, the dynamic model of the TC-DRH-IC S-CO₂ cycle with the modified isentropic efficiency of turbo-machineries, the unsteady flow heat transfer model of heat exchangers and a proportion integration differentiation (PID) controller is established. Second, the peak-load regulation characteristics of the TC-DRH-IC S-CO₂ cycle are analyzed. A comprehensive evaluation method of dynamic control performance considering load change rate, dynamic response time, load rate variation range and cycle efficiency is proposed. Finally, the inventory control method is improved, which can improve the cycle efficiency at low loads. The results show that the improved inventory control method has a rapid practical load change rate of about 10%/min and a wide range of variable-load regulation from 10% to 100%. And the cycle efficiency is improved by 3.67% at 50% of the rated power. The S-CO₂ CFPP has the potential of flexible peak-load regulation.